This invention relates to a tuning control apparatus for an electronic musical instrument.
The pitch of musical tones is usually different with different musical instruments. For example, the pitch of the tone of note A4, for instance, is usually set at slightly different values with natural musical instruments such as the piano, the violin, the flute, etc. and electronic musical instruments. The slight departure from the proper frequency of the note A4, e.g., whether it is 440 Hz or 442 Hz, does not substantially matter so long as an instrument is played solely. However, when a natural musical instrument, e.g., the piano, and an electronic musical instrument are played in concert, it is necessary to tune the instruments to set A4, for instance, to 440 Hz. Since the piano cannot be tuned at the time of performance, the electronic musical instrument is tuned at this time.
The prior art electronic musical instruments are usually provided with a volume switch or slide switch for tuning the instrument. In this case, the oscillation frequency of the main oscillator or VCO (voltage controlled oscillator) is varied by operating the volume switch or slide switch. As the oscillator is one using discrete parts such as LC (coil and capacitor) or RC (resistor and capacitor), it is necessary to provide a comparatively wide frequency range. The characteristics of such discrete parts are subject to changes in long use or with temperature changes, which is undesired from the standpoint of stable and accurate tuning.
With some prior art electronic musical instruments, the above tuning is displayed on the casing of the insturment. In one of such electronic musical instruments, tuning over a 50 percent range is done either upwards or downwards by turning a screw on the casing with a screw driver, and in another case a select switch is used for setting the frequency corresponding to the note A4, for instance, to either 440, 442 or 444 Hz. In the former case, one cannot know the precise tuned value, and also reproducibility is insufficient. In the latter case, limitations are imposed on the range or number of frequencies that can be set.